Heading 030639 applies only when the crustacean species does not fall within the explicitly named headings — rock lobster (030631), Homarus lobster (030632), crabs (030633), Norway lobster (030634), cold-water shrimp (030635), or other shrimp/prawns (030636). Species such as mantis shrimp (Stomatopoda), goose barnacles, or horseshoe crabs used for food would typically land here. Importers uncertain about species classification should seek a CBP binding ruling.

Residual headings can attract CBP scrutiny if importers use them to avoid antidumping or countervailing duty orders that apply to more specifically described products. If the product is functionally a shrimp or prawn, CBP may reclassify it into the appropriate shrimp heading and assess applicable AD/CVD duties. Accurate species documentation — including scientific names on commercial invoices — is the best defense against scope disputes.